Turbo-electric

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UP 18, a locomotive with a turbo-electric drivetrain

A turbo-electric transmission uses electric generators to convert the mechanical energy of a turbine (steam or gas) into electric energy and electric motors to convert it back into mechanical energy to power the driveshafts.

Turbo-electric drives are used in some locomotives (gas turbines, e.g. with the first TGV) and ships (steam and sometimes gas turbines). The advantage of the turbo-electric transmission is that it allows the adaptation of high-speed turning turbines to the slow turning propellers or wheels without the need of a heavy and complex gearbox.

A disadvantage shared with the more common diesel-electric powertrain is that because of the double conversion of mechanical energy to electricity and back more energy gets lost than with a mechanical transmission. Gas turbine are however usually less energy efficient than equally sized diesel engines. Efficiency can be increased, if the exhaust gases of the gas turbine is used to generate steam which powers a steam turbine (Combined cycle/Combined gas and steam).